1. Field of the Invention
The present invention relates to a turbomolecular pump and a turbomolecular pump or vacuum apparatus, and more specifically to a turbomolecular pump and a turbomolecular pump apparatus, which are used as a vacuum apparatus semiconductor manufacturing equipment, an electron microscope or the like.
2. Description of the Related Art
In a case where dry etching, CVD, etc. are performed upon manufacturing a semiconductor or liquid crystal device, a turbomolecular pump apparatus is employed to suck and/or discharge a process gas, which is supplied into a chamber, by means of a turbomolecular pump.
The turbomolecular pump has stator blades and rotor blades which are alternately disposed to provide pairs of the rotor blades and the stator blades in a multistage arrangement. The rotor blades are disposed on a rotor axis that is rotated at high speed, and the stator blades are fixed to a casing.
The rotor blade at each stage includes blades (vanes) provided radially with the inlet port side being tilted toward a traveling direction (direction of rotation). The stator blade at each stage includes blades (vanes) provided radially which are tilted in an opposite direction to the blades of the rotor blade.
The rotor blades impart momentum to gas molecules for delivering them toward the outlet port, and the gas molecules thus transferred are obliquely reflected by the tilted surfaces of the blades of the stator blade, thereby gradually being transferred to the subsequent stage. In such a manner, the gas molecules are sequentially fed from the inlet port side to the outlet port side by the rotor and stator blades at the respective stages, to thereby carry out the discharge.
FIG. 10 is a view showing a sectional configuration of the blades of rotor blades and stator blades in such a gas molecular area.
As shown in FIG. 10, blades 1a of the rotor blade and blades 2a of the stator blade on the inlet port side are respectively formed to have an angle (elevation angles) A of from 30 degrees to 50 degrees with respect to the traveling direction in order to take in the more gas molecules to thereby increase a suction amount thereof.
On the other hand, an elevation angle B of each blade at the outlet port side is set to 25 degree or lower so that it is possible to prevent the gas from reverse-flowing even if the gas pressure rises and mean free distance becomes short.
In other words, the blades 1a, 2a at the inlet port side have a larger tilt angle, while the blades 1b, 2b at the outlet port side have a smaller tilt angle.
In addition, as shown in FIG. 10, the blades at any stages are shaped to have a parallelogram in cross-section in an axial direction. The surfaces of blades that impart the momentum to the gas molecules are planar.
However, as the volume of gas molecules to be discharged is increased, the pressure within the turbomolecular pump is increased with the result that the mean free distance of molecule becomes short. In this case, both blades 1a, 2a on the intake port side, which are specialized their functions to take in the amount of sucking gas, undergo an increased leakage reverse flow of the gas, resulting in lower efficiency. Namely, the exhaust rate is lowered.
Also, in case of the blades 1b, 2b at the outlet port side which specialize in their sealing property (prevention of reverse flow), on the premise that the blades 1a, 2a at the inlet port side have such an effect that the volume of the gas molecules to be taken in is increased, their discharge efficiency is not lowered but the discharge rate is not enhanced. Hence, in the entire pump in which these blades are stacked, the pump performance will be remarkably deteriorated with an increase of the exhaust gas.
Therefore, the present invention has been made in view of the foregoing drawbacks, and has an object of the present invention to provide a turbomolecular pump capable of maintaining a maximum exhaust rate even in a higher pressure.
According to the present invention, there is provided a turbomolecular pump comprising a rotor shaft, a bearing for rotatably supporting the rotor shaft, a motor for driving the rotor shaft supported by the bearing, a rotor body which is disposed on the rotor shaft, rotor blades in a multistage arrangement disposed on the rotor body, the rotor blades each including a plurality of blades extending in a radial direction, and stator blades in a multistage arrangement respectively located between the rotor blades in multistage arrangement, the stator blades each including a plurality of blades extending in a radial direction, wherein a sectional configuration in an axial direction of the blades of one of the rotor blades and the stator blades is formed so that a side facing the travelling direction of the blades includes a plurality of surfaces having different angles, and the surface facing the travelling direction of the blades has an angle on the inlet port side larger than the angle on the outlet port side.
According to the present invention, in a sectional configuration of the blades, a difference between the angles formed by the end surfaces in the plurality of surfaces is 5xc2x0 or more.
According to the present invention, the angles of the surfaces in the sectional configuration of the blades are in a range of 20xc2x0 to 50xc2x0 on the inlet port side, and in a range of 10xc2x0 to 40xc2x0 on the outlet port side, respectively.
According to the present invention, the angles of the surfaces in the sectional configuration of the blades are in a range of 20xc2x0 to 50xc2x0 on the inlet port side, in a range of 10xc2x0 to 40xc2x0 on the intermediate part, and in a range of 10xc2x0 to 90xc2x0 on the outlet port side, respectively.
According to the present invention, in the sectional configuration of the blades, the surfaces on the back side to the travelling direction of the blades include the same angle as that of the surfaces on the front side.
According to the present invention, in the sectional configuration of the blades, at least one of the surfaces on the back side to the travelling direction of the blades includes the angle different from that of the surfaces on the front side.
According to the present invention, in the sectional configuration of the blades on the inlet port side, the surfaces on the back side to the travelling direction of the blades include an angle which is larger by 5xc2x0 or more than that of the surfaces on the front side.
According to the present invention, in the sectional configuration on the outlet port side of the blades, the surfaces on the back side to the travelling direction of the blades include the angle which is larger by 5xc2x0 or more than that of the surfaces on the front side.
According to the present invention, a thread groove pump section is arranged on the outlet port side subsequent to a turbomolecular pump section having the rotor blades and the stator blades.
According to the present invention, there is provided a vacuum apparatus comprising a turbomolecular pump according to the present invention as described above, and a vacuum container connected to an inlet port of the turbomolecular pump, for sucking/discharging gas inside thereof.
That is, according to the present invention, the blades of the rotor blade and the stator blade at each stage are shaped so that the performance involving the elevation angles emphasizing a range from the amount of sucking gas to the capability of preventing the reverse flow can be exerted in the blades at one stage.
As described above, the present invention is so arranged to realize the double effect to increase the amount of sucking gas and to prevent the reverse flow in the blades at one stage. Accordingly, the turbomolecular pump can maintain its maximum discharge rate at a higher pressure.
Further, even if the mean free distance of gas is not larger than the height of the blade (e.g., not larger than 20 nm), the effect involving the suction and the discharge can be obtained in the blades at one stage.